1. Field of the Invention
The present invention relates a fiber material to be used for producing textiles such as knitting fabric, nonwoven fabric, paper and also to the art relating thereto. The invention more particularly relates to an antibacterial fiber to be used in producing such textiles as requiring antibacterial property for destroying micro-organisms including bacteria and molds. The antibacterial products are used where a highly sanitary environment such as a germ-free environment is required, e.g. in medical fields, manufacturing and sales of medical products and food stuff, manufacture of semiconductors, and research/development and application of biotechnology. Some examples of such antibacterial products are textile products to be used in the sanitary environment including various types of work clothes, sheets, masks, dustcloths, wall papers and filter materials including a paper filter for e.g. providing clean air to a highly sanitary environment such as a clean room. The invention also relates to a method of producing the antibacterial fiber as well as to an antibacterial water-treating element using the antibacterial fiber.
2. Description of the Related Art
As described above, the antibacterial fibers have a wide variety of applications. As such antibacterial fiber, the prior art has provided an antibacterial synthetic resin fiber. In producing this synthetic resin fiber, first, an antibacterial material in the form of powder is produced by entrapping silver ion into synthetic or natural zeolite or by causing silver ion to be carried on a synthetic inorganic insoluble matter such as zirconia phosphate. Then, in a spinning bath, this antibacterial material is evenly dispersed within a synthetic resin as a raw material of the fiber. And, this synthetic resin mixed with the antibacterial material is formed into the fiber. The antibacterial synthetic resin fiber provides its antibacterial effect by the silver ion contained in the antibacterial material exposed on the outer surface of the fiber.
The above-described antibacterial synthetic resin fiber comprises the non-elutable type or elution-resistant type in which elution of the antibacterial material hardly occurs or does not occur at all. Thus, the antibacterial synthetic resin fiber is superior in the lastingness and stability of the effect to an antibacterial resin fiber using an elutable organic antibacterial material. However, the conventional antibacterial synthetic resin fiber still suffers drawbacks to be described next.
With the conventional antibacterial synthetic resin fiber, only a portion of the antibacterial material exposing on the outer surface of the synthetic resin fiber can provide the antibacterial effect. The remaining portion of the antibacterial material, i.e. the portion embedded inside the resin provides no contribution at all to the effect. Further, the fiber has a diameter ranging between 8 and 15 .mu.m; whereas, the antibacterial material comprises super fine powder having a particle diameter not exceeding 2 .mu.m, so as not to impair the original properties of the fiber when mixed with the antibacterial material as well as to promote dispersion of the antibacterial material through the resin. Naturally, the amount of the portion of the antibacterial material exposing its silver ion on the outer surface of the fiber is considerably limited and most of the material is embedded inside the resin disadvantageously. More specifically, experiments conducted by the present inventors show that an amount of the antibacterial material capable of providing the effect accounts for only less than 1/3 of the entire amount even with very uniform dispersion of the material in the synthetic resin. The resin needed 1.0 to 5.0% content of the antibacterial material in order to achieve a sufficient antibacterial effect. As a result, the product can provide only limited and unstable antibacterial effect relative to the considerable content of the antibacterial material present in the resin.
Moreover, the availability of the antibacterial material on the fiber surface significantly varies depending on the dispersion condition of the material in the synthetic resin. With uneven dispersion, the amount of antibacterial material exposed on the fiber surface is further limited to provide almost no effect at all. Then, uniform dispersion of the antibacterial material is essential for obtaining a product of stable quality, i.e. antibacterial effect. However, in order to achieve such uniform dispersion, high precision is required in the operations and controls throughout the manufacturing processes from the mixture step of the antibacterial material with the resin to the spinning step of the mixture. All these have tended to result in disadvantageous cost increase.
In addition to the above, the large amount of antibacterial material embedded inside the resin is placed in contact with the surrounding synthetic resin fiber, so that a chemical reaction inevitably occurs between the silver ion of the embedded antibacterial material and the synthetic resin fiber and the reaction can cause disadvantageous discoloration and/or quality deterioration in the resin.
Taking the above-state of the art into consideration, a primary object of the present invention is to provide an improved antibacterial fiber which is economical but can provide antibacterial effect in a stable manner without causing disadvantageous quality change in the fiber.